Terminal blocks for telecommunications and data systems equipment typically comprise a first row of contact elements for connecting incoming wires and a second row of contact elements for connecting outgoing wires. Arranged between the assigned contact elements of the first and second rows are tapping contacts, into which measuring, test and protective plugs can be inserted. The tapping contacts are designed as connecting or disconnecting contacts. The known test and protective plugs are symmetrically constructed, with the housing of the plug covering the contact elements of the first and second rows of contact elements, so that they are not accessible for activation purposes. If the fitted connecting cord of the measuring or test plug happens to be a temporary patch connection and if the temporary patch connection is to be replaced by permanent jumpering, the subscriber connection must first be disconnected by removing the plug before the permanent jumpering can take place.
A further problem is that, when inserting a measuring, protective or test plug, an already existing connection should not be interrupted, since this would otherwise lead to data losses.
DE 34 46 622 A1 discloses a plug insert of a plug for a terminal block, the one-part plug insert comprising a plurality of punched parts that are electrically isolated from one another and form the interconnects, which are encapsulated in a plastic and are consequently embedded in the plastic. The punched parts are preferably formed such that they widen in the region of insertion. This ensures that the plug can be plugged in and pulled out without causing an interruption. A disadvantage of the known plugs is their relatively complex production.
Furthermore, there are known protective plugs for terminal blocks which can be inserted into connecting or disconnecting contacts of a terminal block and are unsymmetrically formed. These plugs substantially comprise an upper housing part and a printed circuit board, which at the same time closes the housing. As a result, the contact elements assigned to subscribers are freely accessible for a placement tool even when the protective plug is inserted. However, owing to the choice of the printed circuit board as the contact element, these plugs have the disadvantage that they cannot be inserted without causing an interruption on account of the circuit board contour with no edge metallization.